Drag and drop stops working in Windows 7 and 8

I've been struggling with this problem for a long time, and never really found a solution. Basically (and very randomly) drag and drop would stop working on my workstation. This includes dragging emails in Outlook (2007, 2010, 2013), dragging files in explorer, and even resizing columns in certain folders/views/apps. What threw me the most is that the issue persisted when i upgraded to a new workstation with a fresh OS, and also across Windows 7 and 8. I do have a lot of apps, so it's very possible one of them is to blame. A reboot would always fix it, but that's obviously annoying. Anyways, the fix: Go to explorer, click on a file, and press the escape key. That's it. I have yet to investigate why it works, but it works. The working theory is that somewhere a file is stuck in the drag state, and windows doesn't let you drag additional items. Hitting escape must clear that out and let you do it again.